Liquid developers

ABSTRACT

A toner or developer for electrostatic images including a carrier liquid and insoluble marking particles. The carrier liquid comprises or includes a polybutene. The polybutene may be present in a range of 20 to 98 percent by weight. The carrier liquid can also includes one or a blend of other carrier liquids selected from aliphatic hydrocarbons, aromatic hydrocarbons, chlorinated solvents, silicone fluids and vegetable oils. The insoluble marking particle is present in the range of 2 to 40 percent by weight of the toner or developer.

TECHNICAL FIELD

[0001] This invention relates to liquid developers suitable forelectrostatography.

BACKGROUND ART

[0002] Electrostatography is a term used to describe various non-impactprinting processes which involve the creation of a visible image by theattraction of charged imaging particles or marking particles to chargesites present on a substrate. Such charge sites, forming what is usuallytermed a latent image can be transiently supported on photoconductors orpure dielectrics and may be rendered visible in situ or be transferredto another substrate to be developed in that location. Additionally suchcharged sites may be the reflection of those structured charges existingwithin a permanently polarised material as in the case withferroelectrics or other electrets.

[0003] Electrostatography encompasses those processes normally known aselectrophotography and electrography.

[0004] In general, a liquid developer, or toner, for electrostatographyis prepared by dispersing an inorganic or organic colourant such as ironoxide, carbon black, nigrosine, phthalocyanine blue, benzidine yellow,quinacridone pink and the like into a liquid vehicle which may containdissolved or dispersed therein synthetically or naturally occurringpolymers such as acrylics, alkyds, rosins, rosin esters, epoxies,polyvinyl acetate, styrene-butadiene etc. Additionally to affect orenhance electrostatic charge on such dispersed particles additives knownas charge directors or charge control agents may be included. Suchmaterials can be metallic soaps, fatty acids, lecithin, organicphosphorus compounds, succinimides, sulphosuccinates etc.

[0005] In such developers, whether positively or negatively charged,there is one ingredient of common generic character, namely the carrierliquid. Since the beginning of the history of liquid toners, it has beenrecognised that certain electrical properties of the carrier liquid aremandatory requirements for the effective functioning of a conventionalelectrostatographic liquid development process. The mandatoryrequirement is low electrical conductivity but other requirements havealso became obvious, such as the need for low toxicity, increased firesafety, low solvent power, low odour etc. For these reasons,isoparaffinic-hydrocarbons such as the Isopar® range manufactured byExxon Corporation, the Shellsol® range manufactured by Shell Chemicaland the Soltrol® range manufactured by Phillips Petroleum have becomethe industry standards for liquid toner carriers.

[0006] In more recent times, however, certain deficiencies in theseisoparaffins have become apparent. Environmental concerns have placedliquid development processes under increasing pressure to reduce oreliminate volatile emissions. Flammability has also become importantregarding the more stringent transport regulations existing andanticipated worldwide.

[0007] New designs of image fusing stations are also placing increasedimportance on the thermal stability of carrier liquids.

[0008] In order to overcome these limitations other materials which maybe applicable as carrier liquids for liquid toners have beeninvestigated.

[0009] It has surprisingly been found that polybutenes can function ascarrier liquids.

[0010] In one form therefore the invention is said to reside in a toneror developer for electrostatic images including a carrier liquid andinsoluble marking particles characterised by the carrier liquid being apolybutene.

[0011] In an alternative form the invention may be said to reside in aliquid toner or developer for electrostatic graphic images characterisedby a carrier liquid comprising or including polybutene.

[0012] Polybutene is a synthetic hydrocarbon polymer made by thepolymerisation of isobutene (also known as “isobutylene”). Another namefor polybutene is polyisobutylene. Throughout this specification theterm polybutene will be used to refer to this range of compounds.

[0013] Polybutenes range from light mobile liquids to extremely viscousgels. Basically the longer the polymer chain is allowed to grow, thehigher the viscosity. Polybutenes have many of the characteristics ofiso-paraffinic hydrocarbons and non-branched paraffin oils but areclassified as a true polymer rather than a hydrocarbon liquid.

[0014] The properties of polybutenes which make them of interest in thefield of liquid developers for electrostatography include:

[0015] 1. Polybutenes are free from aromatics and hence are generallyregarded as safe.

[0016] 2. Polybutenes are non-staining and essentially water white incolour.

[0017] 3. Polybutenes are available in a wide range of viscosities.

[0018] 4. Polybutenes are chemically very stable with good resistance tooxidation and chemicals at normal temperatures.

[0019] 5. Polybutenes have a high electrical resistivity.

[0020] 6. Polybutenes are completely hydrophobic.

[0021] It will be seen that by this invention a liquid developer ortoner can be proposed which may have a range of viscosities dependingupon the required application.

[0022] In such liquid developers or toners the polybutene may be presentin a range of 20 to 98 percent by weight of the toner.

[0023] Blends of other carrier liquids could be used in conjunction withthe polybutene carrier liquid. The other carrier liquids may be one ormore of aliphatic hydrocarbons, aromatic hydrocarbons, chlorinatedsolvents, silicone fluids and vegetable oils.

[0024] As indicated above the liquid developer or toner may also includean organic or inorganic insoluble marking particle and such a markingparticle may be present in the range of 2 to 40 percent.

[0025] Marking particles that are insoluble in the carrier liquid may beselected upon their particular proposed end use. Examples of markingparticles include inorganic pigments such as carbon blacks, silica,alumina, titanium dioxide, magnetic iron oxide, or organic pigments suchas phthalocyanine blue, alkali and reflex blue, phthalocyanine green,diarylide yellow, arylamide yellow, azo and diazo yellow, azo red,rubine toner, quinacridone red, basic dye complexes, lake red, orfluorescent pigments and dyestuffs such as basic dyes and spirit solubledyes, or combinations thereof. Other materials, as would be understoodby those skilled in the art, could be used as marking particles.

[0026] The liquid developer or toner may also include a charge controlagent to impart or enhance an electrostatic charge on the insolubleparticles in the toner or developer. These charge control agents may beselected from metallic soaps, fatty acids, lecithin, organic phosphoruscompounds, succinimides, sulphosuccinimides or the like.

[0027] The charge control agent may be present in a range of 0.01 to 5percent by weight of the toner when used.

[0028] The liquid developer or toner may also include a dispersant whichcan be selected, for example, from the Solsperse range of polymerichyperdispersants including 13940 made by Avecia; amino-siliconesincluding Finish WR1600 made by Wacker Chemicals; polymeric oiladditives including Plexol made by Rohm and Haas; polymeric petroleumadditives including FOA-2 made by Dupont; alkylated poly vinylpyrrolidones including Antaron AV220 made by ISP Technologies;multi-functional pigment dispersing agents including Disperse Ayd 1 madeby Elementis DCP Inc.

[0029] The dispersant may be present in a range of 0.1 to 20 percent byweight of the toner when used.

[0030] Polybutenes range in viscosity from light mobile liquids toextremely viscous grades, and hence may be used for high viscosity orlow viscosity type liquid developers. The polybutene carrier liquid mayhave a range of viscosity from 10 centistokes to 50,000 centistokes at100° C.

[0031] The liquid toner or developer formulation according to thisinvention may include other components as are known in the art includingpreservatives, viscosity modifiers and binders.

[0032] This then generally describes the invention but to assist withunderstanding, reference will now be made to examples of liquid tonersincorporating polybutylene as the carrier liquid.

[0033] The various examples were tested using an electrostatic printerof the type described in patent specification WO095/08792.

EXAMPLE 1

[0034] A liquid developer was prepared having the following composition:Irgalite Blue LGLD 25 grams Epikote 1001 100 grams

[0035] The blue pigment and epoxy resin were blended together at 60° C.using a Buss hot-melt extruder and allowed to cool. The blue pigment andresin composite was then crushed to a coarse powder and added to a 2litre ceramic ball jar together with: Aluminium stearate 1 gramSolsperse 13940 10 grams Napvis 07 364 grams

[0036] This mixture was then ball milled for 7 days to form a viscous,blue dispersion with a total marking particle content of 25% w/w.

[0037] Irgalite Blue is a CI Pigment Blue 15:3 made by Ciba SpecialtyChemicals Inc. Epikote 1001 is a low molecular weight solid epoxy resinmade by Shell Chemicals Aluminium stearate is a thickening agent made byAsia Pacific Specialty Chemicals Limited.

[0038] Solsperse 13940 is a polyamine/fatty acid condensation polymerdispersing agent manufactured by Avecia.

[0039] Napvis 07 is a polyisobutylene manufactured by BP Chemicals andhaving a viscosity of 13 centistokes at 100° C.

[0040] The manufactured toner was found to have a viscosity of 500 mPa.sand an average particle size of 1.1 micrometers.

[0041] This toner was used in the printer where a high density image wasprinted on paper substrate with no background staining.

EXAMPLE 2

[0042] A liquid developer was prepared having the following composition:Irgalite Blue LGLD 20 grams Epikote 1001 80 grams

[0043] The blue pigment and epoxy resin were blended together at 60° C.using a Buss hot-melt extruder and allowed to cool. The blue pigment andresin composite was then crushed to a coarse powder and added to a 2litre ceramic ball jar together with: Aluminium stearate 1 gramSolsperse 13940 10 grams Napvis 07 389 grams

[0044] This mixture was then ball milled for 7 days to form a viscous,blue dispersion with a total marking particle content of 20% w/w.

[0045] The manufactured toner was found to have a viscosity of 440 mPa.sand an average particle size of 1.0 micrometers.

[0046] This toner was used in the printer where a high density image wasprinted on aluminium sheet substrate with no background staining.

EXAMPLE 3

[0047] A liquid developer was prepared having the following composition:Irgalite Blue LGLD 10 grams Epikote 1001 40 grams

[0048] The blue pigment and epoxy resin were blended together at 60° C.using a Buss hot-melt extruder and allowed to cool. The blue pigment andresin composite was then crushed to a coarse powder and added to a 2litre ceramic ball jar together with: Aluminium stearate 1 gramSolsperse 13940 10 grams Napvis 07 439 grams

[0049] This mixture was then ball milled for 7 days to form a viscous,blue dispersion with a total marking particle content of 10% w/w.

[0050] The manufactured toner was found to have a viscosity of 300 mPa.sand an average particle size of 0.9 micrometers.

[0051] This toner was used in the printer where a medium density imagewas printed on aluminium sheet substrate with no background staining.

EXAMPLE 4

[0052] A liquid developer was prepared having the following composition:Irgalite Blue LGLD 20 grams Epikote 1001 80 grams

[0053] The blue pigment and epoxy resin were blended together at 60° C.using a Buss hot-melt extruder and allowed to cool. The blue pigment andresin composite was then crushed to a coarse powder and added to a 2litre ceramic ball jar together with: Aluminium stearate 1 gramSolsperse 13940 10 grams Napvis 07 289 grams Isopar L 100 grams

[0054] This mixture was then ball milled for 7 days to form a viscous,blue dispersion with a total marking particle content of 20% w/w.

[0055] Isopar L is an isoparaffinic hydrocarbon liquid made by ExxonChemical.

[0056] The manufactured toner was found to have a viscosity of 70 mPa.sand an average particle size of 0.8 micrometers.

[0057] This toner was used in the printer where a high density image wasprinted on aluminium sheet substrate with no background staining.

EXAMPLE 5

[0058] A liquid developer was prepared having the following composition:Irgalite Blue LGLD 20 grams Epikote 1001 80 grams

[0059] The blue pigment and epoxy resin were blended together at 60° C.using a Buss hot-melt extruder and allowed to cool. The blue pigment andresin composite was then crushed to a coarse powder and added to a 2litre ceramic ball jar together with: Aluminium stearate 1 gramSolsperse 13940 10 grams Hyvis 2000 100 grams Isopar L 289 grams

[0060] This mixture was then ball milled for 7 days to form a viscous,blue dispersion with a total marking particle content of 20% w/w.

[0061] Hyvis 2000 is a polyisobutylene manufactured by BP Chemicals andhaving a viscosity of 40500 centistokes at 100° C.

[0062] The manufactured toner was found to have a viscosity of 95 mPa.sand an average particle size of 0.8 micrometers.

[0063] This toner was used in the printer where a high density image wasprinted on aluminium sheet substrate with no background staining.

EXAMPLE 6

[0064] A liquid developer was prepared having the following composition:Permanent yellow DHG01 20 grams Epikote 1001 80 grams

[0065] The yellow pigment and epoxy resin were blended together at 60°C. using a Buss hot-melt extruder and allowed to cool. The yellowpigment and resin composite was then crushed to a coarse powder andadded to a 2 litre ceramic ball jar together with: Aluminium stearate 1gram Solsperse 13940 10 grams Napvis 07 389 grams

[0066] This mixture was then ball milled for 7 days to form a viscous,yellow dispersion with a total marking particle content of 20% w/w.

[0067] Permanent yellow DHG01 is a CI Pigment yellow 12 made by Clariant(Australia) Pty Ltd.

[0068] The manufactured toner was found to have a viscosity of 290 mPa.sand an average particle size of 2.0 micrometers.

[0069] This toner was used in the printer where a medium density imagewas printed on aluminium sheet substrate with no background staining.

EXAMPLE 7

[0070] A liquid developer was prepared having the following composition:Hostaperm pink E 20 grams Epikote 1001 80 grams

[0071] The red pigment and epoxy resin were blended together at 60° C.using a Buss hot-melt extruder and allowed to cool. The red pigment andresin composite was then crushed to a coarse powder and added to a 2litre ceramic ball jar together with: Aluminium stearate 1 gramSolsperse 13940 10 grams Napvis 07 389 grams

[0072] This mixture was then ball milled for 7 days to form a viscous,red dispersion with a total marking particle content of 20% w/w.

[0073] Hostaperm pink E is a CI Pigment red 122 made by Hoechst.

[0074] The manufactured toner was found to have a viscosity of 300 mPa.sand an average particle size of 1.0 micrometers.

[0075] This toner was used in the printer where a medium density imagewas printed on aluminium sheet substrate with no background staining.

EXAMPLE 8

[0076] Hostaperm Pink E 20 grams Fine Tone 6694, F 80 grams

[0077] The red pigment and polyester resin were blended together at 100°C. using a Buss hot-melt extruder and allowed to cool. The red pigmentand resin composite was then crushed to a coarse powder and added to a 2litre ceramic ball jar together with: Napvis 07 400 g Basic BariumPetronate 2.5 g

[0078] This mixture was then ball milled for 7 days to form a viscous,red dispersion with a total marking particle content of 20% w/w.

[0079] Basic Barium Petronate is a charge control agent made by WitcoCorporation. Fine Tone 6694 is a polyester resin made by Reichhold Inc.

[0080] The manufactured toner was found to have a viscosity of 600 mPa.sand an average particle size of 2.5 micrometers.

[0081] This toner was used in the printer where a medium density imagewas printed on paper substrate with no background staining.

[0082] Throughout this specification various indications have been givenas to the scope of the invention but the invention is not limited to anyone of these but may reside in two or more combined together. Theexamples are given for illustration only and not for limitation.

[0083] Throughout this specification and the claims that follow unlessthe context requires otherwise, the words ‘comprise’ and ‘include’ andvariations such as ‘comprising’ and ‘including’ will be understood toimply the inclusion of a stated integer or group of integers but not theexclusion of any other integer or group of integers.

1/ A toner or developer for electrostatic images including a carrierliquid and insoluble marking particles characterised by the carrierliquid comprising or including a polybutene. 2/ A toner or developer forelectrostatic images as in claim 1 wherein the polybutene is present ina range of 20 to 98 percent by weight. 3/ A toner or developer forelectrostatic images as in claim 1 wherein the carrier liquid includesone or a blend of other carrier liquids selected from the groupcomprising aliphatic hydrocarbons, aromatic hydrocarbons, chlorinatedsolvents, silicone fluids and vegetable oils. 4/ A toner or developerfor electrostatic images as in claim 1 wherein the insoluble markingparticle is selected from the group comprising an organic or inorganicinsoluble marking particle. 5/ A toner or developer for electrostaticimages as in claim 1 wherein the insoluble marking particle is presentin the range of 2 to 40 percent by weight of the toner or developer. 6/A toner or developer for electrostatic images as in claim 1 wherein theinsoluble marking particle is selected from the group comprisinginorganic pigments such as carbon blacks, silica, alumina, titaniumdioxide, magnetic iron oxide, or organic pigments such as phthalocyanineblue, alkali and reflex blue, phthalocyanine green, diarylide yellow,arylamide yellow, azo and diazo yellow, azo red, rubine toner,quinacridone red, basic dye complexes, lake red, or fluorescent pigmentsand dyestuffs such as basic dyes and spirit soluble dyes, orcombinations thereof. 7/ A toner or developer for electrostatic imagesas in claim 1 further including a charge control agent to impart orenhance an electrostatic charge on the insoluble particles in the toneror developer. 8/ A toner or developer for electrostatic images as inclaim 7 wherein the charge control agent is selected from the groupcomprising metallic soaps, fatty acids, lecithin, organic phosphoruscompounds, succinimides or sulphosuccinimides. 9/ A toner or developerfor electrostatic images as in claim 7 wherein the charge control agentis present in a range of 0.01 to 5 percent by weight of the toner ordeveloper. 10/ A toner or developer for electrostatic images as in claim1 further including a dispersant. 11/ A toner or developer forelectrostatic images as in claim 10 wherein the dispersant is selectedfrom the group comprising polymeric hyperdispersants, amino-silicones,polymeric oil additives, polymeric petroleum additives, alkylated polyvinyl pyrrolidones and multi-functional pigment dispersing agents. 12/ Atoner or developer for electrostatic images as in claim 10 wherein thedispersant is selected from the group comprising the Solsperse range ofpolymeric hyperdispersants including 13940 made by Avecia;amino-silicones including Finish WR1600 made by Wacker Chemicals;polymeric oil additives including Plexol made by Rohm and Haas;polymeric petroleum additives including FOA-2 made by Dupont; alkylatedpoly vinyl pyrrolidones including Antaron AV220 made by ISPTechnologies; multi-functional pigment dispersing agents includingDisperse Ayd 1 made by Elementis DCP Inc. 13/ A toner or developer forelectrostatic images as in claim 10 wherein the dispersant is present ina range of 0.1 to 20 percent weight of the toner or developer. 14/ Atoner or developer for electrostatic images as in claim 1 wherein thepolybutene carrier liquid has a range of viscosity from 10 centistokesto 50,000 centistokes at 100° C., and hence may be used for highviscosity or low viscosity type liquid developers. 15/ A toner ordeveloper for electrostatic images as in claim 1 further including othercomponents selected from the group comprising preservatives, viscositymodifiers and binders.